Nonvolatile memories are semiconductor memories that retain their contents when unpowered. Nonvolatile memories are used for storage in electronic devices such as digital cameras, cellular telephones, and music players, as well as in general computer systems, embedded systems and other electronic devices that require persistent storage. Nonvolatile semiconductor memories can take the form of removable and portable memory cards or other memory modules, can be integrated into other types of circuits or devices, or can take any other desired form. Nonvolatile semiconductor memories are becoming more prevalent because of their advantages of small size and persistence, having no moving parts, and low power consumption.
Flash memory is a common type of nonvolatile memory used in a variety of devices. Flash memory has an architecture that can result in long access, erase, and write times. The operational speeds of electronic devices and storage demands of users are rapidly increasing. Flash memory is proving, in many instances, to be inadequate for nonvolatile memory needs. Additionally, volatile memories (such as random access memory (RAM)) can potentially be replaced by nonvolatile memories if the speeds of nonvolatile memories are increased to meet the requirements for RAM and other applications currently using volatile memories.
Thus, what is needed is a new type of nonvolatile memory. Memories that include elements which exhibit changes in resistive states in response to the application of voltages have been described. These memories typically have operational and durability limitations. Therefore, a resistive-switching memory with improved operational and durability characteristics is desired.